Why Some People Develop Celiac Disease Instead of Type One Diabetes?

Celiac.com 03/19/2026 - This study explored why two autoimmune diseases that often share genetic risk factors—celiac disease and type one diabetes—do not always develop together. Although both conditions are strongly linked to the same immune-related genes, many people develop only one of them. The researchers set out to understand whether subtle genetic differences inside a well-known immune gene region could help explain this split in disease outcomes

Background: Shared Genetics, Different Outcomes

Celiac disease and type one diabetes are both autoimmune conditions, meaning the immune system mistakenly attacks the body’s own tissues. In celiac disease, the immune system damages the lining of the small intestine when gluten is eaten. In type one diabetes, immune cells destroy insulin-producing cells in the pancreas.

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Both diseases are strongly linked to the same immune gene region on chromosome six. This region controls how the immune system recognizes proteins. Many people who carry these high-risk genes never develop either disease, while others develop only one. This mismatch has long puzzled researchers and clinicians.

The Focus on a Small but Important Genetic Region

The researchers focused on a tiny section of a gene involved in immune signaling. Although this gene was once considered stable and unimportant for disease risk, earlier work suggested that small variations in this region could significantly influence the likelihood of developing type one diabetes.

In this study, scientists examined three closely grouped genetic markers inherited together. These markers form distinct patterns that can subtly change how immune-related genes behave. The research team analyzed how these patterns affected disease development over time.

Following Children at Risk from Birth

The study followed thousands of children enrolled at birth because they carried genetic risk factors for autoimmune disease. These children were regularly monitored for immune activity, including early immune markers that appear before symptoms of disease.

Over more than a decade of follow-up, researchers tracked which children developed immune markers linked to type one diabetes, which developed markers linked to celiac disease, and which eventually received a clinical diagnosis.

A Protective Effect for Type One Diabetes

One of the most striking findings was that a specific genetic pattern significantly reduced the risk of developing type one diabetes. Children carrying this pattern were less likely to develop early immune markers against insulin and less likely to progress to full disease.

This protective effect was strongest in children who otherwise carried the highest known genetic risk for type one diabetes. The results confirmed earlier findings and demonstrated that even within high-risk groups, genetic fine details matter.

The Unexpected Increase in Celiac Disease Risk

While this genetic pattern appeared protective for type one diabetes, it had the opposite effect for celiac disease. Children carrying the same pattern were more likely to develop immune reactions against gluten and more likely to receive a celiac disease diagnosis.

This opposite influence was unexpected because the two diseases are usually thought to share similar genetic drivers. The finding suggests that certain immune pathways may push the body toward one autoimmune target while pulling it away from another.

Early Immune Signals Reveal Different Disease Paths

The study also examined early immune markers that appear before disease symptoms. For type one diabetes, the protective genetic pattern mainly reduced immune responses directed at insulin, which are often seen early in childhood.

For celiac disease, the same genetic pattern increased the likelihood of developing antibodies linked to intestinal immune damage. These early signals often appear years before symptoms, suggesting that the immune system’s direction may be set very early in life.

Clues from the Complement System

To understand why one genetic pattern could have opposite effects, the researchers examined immune gene activity in blood cells. They found differences in genes involved in the complement system, which plays a role in immune defense and inflammation.

Some versions of the genetic pattern were associated with reduced activity or missing copies of certain complement genes, while others showed increased activity of related genes. These differences may alter how the immune system clears immune complexes or responds to environmental triggers.

Why These Findings Matter

This research highlights how small genetic differences can significantly influence autoimmune disease outcomes. Rather than viewing celiac disease and type one diabetes as nearly identical in genetic risk, the study shows that risk can be redirected in opposite directions by subtle variations.

These findings may help improve risk prediction models. Knowing whether a child with high-risk immune genes is more likely to develop celiac disease rather than type one diabetes could guide monitoring strategies and early interventions.

What This Means for People with Celiac Disease

For individuals and families affected by celiac disease, this study offers important insight. It reinforces that celiac disease is not simply a byproduct of shared autoimmune risk but may involve distinct immune pathways that deserve focused attention.

Understanding these genetic differences could eventually lead to earlier identification of at-risk individuals, better screening strategies, and more personalized approaches to prevention and care. For people living with celiac disease, this research helps explain why the disease can appear independently, even in families where multiple autoimmune risks are present.

Read more at: elifesciences.org